Like many tech-savvy people in China, Kai-Fu Lee spent some time Friday tinkering with Google’s new feature, which allows users to see in advance which search terms might trigger a block from the mainland’s system of online censorship. Lee, who previously headed Google China before leaving in 2009 to start a Beijing-based venture-capital firm, did a search on himself. Google’s service indicated that his surname, written as 李 in Chinese, could cause a problem. Searching for it “may temporarily break your connection to Google,” the service warned. “This interruption is outside Google’s control.”

“This prompt is interesting!” Lee wrote on Sina Weibo, a Twitter-like microblog service, where he has 13.4 million followers. “You could add a line: ‘Suggest you consider a change of surname. Those you can search for include Zhang, Sun, Jiang …'” In a few short words, Lee captured the brilliance and futility of Google’s new feature. It shows with a new degree of transparency just what might set off China’s Great Firewall. But it gives you limited options to deal with it.

Lee, or Li as it is romanized in mainland China’s Pinyin system, is one of the most common surnames in greater China. It’s shared by the late actor Bruce Lee, Hong Kong tycoon Li Ka-shing and tennis player Li Na. The Li who likely tripped the warning, though, is Li Changchun, a member of China’s top-level Politburo standing committee and the official charged with running the country’s propaganda and censorship apparatuses. (Another possibility is Chinese Vice Premier Li Keqiang, the man expected to take over for Premier Wen Jiabao during the leadership transition that begins this fall.) Chinese Web users who put the Google tool through its paces found that the surname of every Politburo Standing Committee member triggered a warning.

Google has had a tortuous history in China. Under Kai-Fu Lee, it introduced google.cn, a search engine that complied with Chinese censorship, in 2006. Then, in January 2010, it announced that it was going to stop censoring its Chinese search results in response to a sophisticated cyberattack on its digital infrastructure. Two months later, the company began to route search queries through Hong Kong, which isn’t subject to online restrictions like mainland China. These searches aren’t restricted by Chinese censorship requirements, but if you search for a sensitive term you will likely get an error message — “The connection has been reset” or “This Web page is not available” — and then be unable to use Google for several minutes. Local competitor Baidu censors its search results, which means that users won’t see error messages or be blocked from using the site, but they will also be steered from content the government deems objectionable. In the battle for users, Baidu’s ease of use has won out over Google’s freedom. Baidu held 78.5% of the Chinese search market for the first quarter of 2012 vs. 16.6% for Google, according to Chinese research firm Analysys International.

In a blog post announcing its new feature for the Chinese market, Alan Eustace, Google’s senior vice president of knowledge, said the prompts should help mainland Chinese users. “So starting today we’ll notify users in mainland China when they enter a key word that may cause connection issues,” he wrote. “By prompting people to revise their queries, we hope to reduce these disruptions and improve our user experience from mainland China.” One possible work-around it mentioned was writing the romanized version of sensitive words — Li for 李, for instance. Eustace avoided mentioning China’s Great Firewall, saying merely “we’ve had a lot of feedback that Google Search from mainland China can be inconsistent and unreliable.” But Chinese authorities probably won’t appreciate the service, no matter how it is described. On Sina Weibo, many posts mentioning it were censored on Friday, but as of 6 p.m., Lee’s was still up and had been forwarded by more than 3,000 Weibo users.